1. Technical Field
The present invention relates to retaining walls and particularly to stackable precast concrete bin-type structures for creating retaining walls.
2. Background Information
A gravity retaining wall is the simplest and probably the oldest known kind of retaining wall. This type of wall relies on the mass of the wall material and a configuration that normally decreases in thickness from base to top to resist the overturning force exerted by the pressure of earth behind it. Gravity retaining walls are usually made of stone, concrete block, or monolithic concrete poured at the site.
Another type of retaining wall is a cribbing wall constructed from interlocking timbers or precast concrete elements. Examples of concrete cribbing arrangements are disclosed in U.S. Pat. Nos. 2,149,957 of Dawson and 2,828,613 of Wilson. The Dawson cribbing wall is assembled from three different rigid precast concrete elements: stretchers, headers, and anchors. The stretchers and headers are elongated straight elements having interengaging socket-and-lug ends that can be locked together by impaling rods. The stretchers form the face of the wall, and the headers extend perpendicularly to the face into the bank behind the wall. The anchors are U-shaped elements that interengage with the inner ends of the headers to create a hollow box-like structure, or crib. Each rigid element is cast separately, and the cribbing is assembled piece-by-piece at the site. The Wilson cribbing assembly is made up of identical precast concrete blocks. The blocks are notched so that they can be assembled like a log cabin to provide a zig-zag, a triangular, or a square configuration.
A special type of retaining wall structure has been developed for sloping banks. Examples of this type are terraced retaining wall assemblies shown in U.S. Pat. Nos. 3,343,301 of Adelman, 2,960,797 and 3,444,694 of Frehner, and 3,269,125 of Moore. Adelman provides individual rectangular blocks that are small enough and light enough to be carried by one person. Each block has a semicylindrical shoulder at each end, the shoulder having a pivot hole, so that the blocks can be hinged together on upright pins in a zig-zag arrangement. Successive courses of the blocks are arranged in stepwise setback fashion to create a terraced retaining wall. The sole anchoring of the wall is provided by the hinge pins; the blocks form only the face of the wall. The Frehner and Moore structures use rigid two-sided angled blocks of an open V or U shape to create a terraced wall similar in appearance to the Adelman wall.
Still another type of retaining structure that is suitable for horizontal or slightly sloped surfaces is a flexible revetment mat, as disclosed by U.S. Pat. Nos. 2,674,856 of Louckes, 1,847,852 of Upson, and 1,847,868 of Everham. In the Louckes structure, which is a typical example, a number of slightly spaced concrete blocks are cast in a rectangular array and are reinforced and bound together by a continuous structure of wire fabric. The resulting mat has the necessary flexibility to adjust itself to irregularities of a river bank or bed. This type of mat is not usable as retaining wall on a steep slope, however, because it relies only on the force of gravity to hold it against the earth surface.
More recently, precast rigid so-called bin-type elements have been developed that can be stacked to make a vertical retaining wall. In most systems, individual units interlock with other units to form an integral structure of open bins which are subsequently backfilled with gravel to add the necessary mass to the wall structure. These elements are of various shapes, but they typically have a flat face panel, an anchor member, and at least one web or spacer extending between the rear of the face panel and the anchor. These elements are normally designed to be stacked only in a straight line. In addition, they require relatively large, complex, and expensive molds, and because of their rigid, three-dimensional shape, they take up a large amount of space for storage and shipping relative to the wall area provided by the face panel.